Rotary Car Club - What could cause coil not to ground?

Basically I'm getting no spark. I have done a lot of electrical testing and gone through the whole system quite thoroughly and think I have narrowed the no-spark issue down to one thing.

Apparently if you have everything hooked up and jumper the ground pin on any coil plug, and test voltage with a multimeter (one lead on pin/paper clip/whatever you are using to jumper the ground at the plug, and one lead to a ground/chassis) you should see fluctuating voltage. So basically 12v-0v-12v-0v-12v-0v as the igniter grounds the coil. I'm seeing very good voltage at the plug (16v, 13 when cranking) but it never grounds.

I haven't actually tested my coils but I'm convinced they aren't the problem because they rarely fail and they were Working fine the last time I used them. So as far as I'm concerned, once the coil starts grounding I should see spark.

Problem- I don't have a heck of a lot of time to work on this car, only really Saturdays and Friday nights so I want to make the most of that time and have just a solid list of things to check so I'm not just dicking around for hours trying to BS myself into thinking I know what the problem could be.

So I got a list of things going here and I just want to know if there's anything else I can add. So far I've got:

-Make sure igniter is grounded (this is my #1 suspect)
-check ecu is grounded properly
-check ground on coil harness
-check engine to chassis ground
-make sure crank sensors are working properly (no clue what proper functioning voltage and amperage fluctuations are but I can get a running car to compare to)
-test using stock ecu (to eliminate the ecu as a potential problem)
-test without twin power (again, shouldn't be the problem since power is still going to coils)

Is there anything else I can add to the list?